Frank, Sorry for the confusion. I thought that turning off cache using hdparm -W 0 /dev/sdx takes effect right away and in case of non-raid controllers and Seagate or Micron SSDs I would see a difference starting fio benchmark right after executing hdparm. So I wonder it makes a difference whether cache turned off before OSD started or after.
On Tue, Jan 21, 2020, 2:07 AM Frank Schilder <fr...@dtu.dk> wrote: > > So hdparam -W 0 /dev/sdx doesn't work or it makes no difference? > > I wrote "We found the raw throughput in fio benchmarks to be very > different for write-cache enabled and disabled, exactly as explained in the > performance article.", so yes, it makes a huge difference. > > > Also I am not sure I understand why it should happen before OSD have > been started. > > At least in my experience hdparam does it to hardware regardless. > > I'm not sure I understand this question. Ideally it happens at boot time > and if this doesn't work, at least sometimes before the OSD is started. Why > and how else would one want this to happen? > > Best regards, > > ================= > Frank Schilder > AIT Risø Campus > Bygning 109, rum S14 >
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